Field of the Invention
The present invention relates to an engine cooling system, an electronic thermostat control system and a control method for the same which may actively control coolant temperature according to an operation condition of a vehicle and implement fault diagnosis so as to satisfy OBD (On Board Diagonostics) regulations.
Description of Related Art
In a combustion stroke, high temperature about 2000-2500° C. generated within an engine is transmitted to cylinder walls, a cylinder head, a piston valve and so on so as to deteriorate strength of elements. So, breakdown, lift-shortening, knocking, early ignition may occur.
If the engine is over cooled for solving the above problems, efficiency of the engine may be deteriorated and fuel consumption may be increased.
So, a thermostat is provided to an engine for maintaining coolant temperature within about 80-90° C.
The thermostat is disposed between the engine and the radiator and changes displacement of a valve according to changes of coolant temperature, and thus flowing amount flowing through the radiator is adjusted. Accordingly, the coolant is maintained within appropriate temperature, for example about 80-90° C.
That is, the thermostat changes the displacement of the valve for the coolant to flow through the radiator when the coolant temperature is higher than a predetermined temperature, and the valve is closed to bypass the radiator if the coolant temperature is less than a predetermined temperature.
A mechanical thermostat expands wax provided thereto depending only on a temperature of the coolant, and therefore, the mechanical thermostat may not be operated actively against changes of the driving circumstances of the vehicle.
Furthermore, while cooling systems of a vehicle are generally designed to satisfy the toughest driving condition, such as, a full load, for example, actual driving is generally conducted within about 70% of a full load. Accordingly, over cooling of the engine often occurs, which results in a decrease in engine efficiency, an increase in fuel consumption, and an increase in harmful exhaust particles.
In order to overcome these drawbacks, several attempts have been made to provide an adjustable electronic thermostat valve that optimizes the coolant temperature.
One such electronic thermostat is an electronic thermostat valve having a heating means that cooperates with expansion of a wax element. The electronic thermostat valve includes a plug for supplying electronic power and a heater for heating the wax.
The electric power supplied to the heater changes upon driving conditions such as speed of a vehicle, temperature of intake air, and load conditions.
However, a drawback of this electronic thermostat is that the thermostat may not actively response to variable conditions such as operation conditions of a vehicle, rising or descending of coolant temperature and so on.
Also, diagnosis functions for detecting malfunction of the cooling system is not included and thus it may not satisfy OBD regulations.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.